Chicken sickness getting worse!! I need help!!!

[Kayajost]

I have a polish chicken and I'm not sure what's wrong with her. She is sick and just sits around. She is extremely dirty and there seems to be snot filling up inside of her nostril so now it's really big. I have no clue what to do and I need help :/

 

[Wyorp Rock]

Can you post some photos?
Sounds like a respiratory illness.
Any discharge from the eyes, wheezing, sneezing, coughing etc.?
I would separate her so you can monitor/treat her. A sick chicken sometimes will also become dehydrated so she may need a little help with that.
When you say she is extremely dirty, what is it from, her behind or is she laying in poo or does she have a "rotten" odor to her?
http://edis.ifas.ufl.edu/ps044